A known electronic engine control system comprises a processor-based engine controller that processes data from various sources to develop control data for controlling certain functions of the engine, including fueling of the engine by injection of fuel into engine combustion chambers. Control of engine fueling extends to both the duration of an injection of fuel and the timing of fuel injection so that the control system thereby sets both the amount of fuel injected and the time at which injection occurs during an engine cycle.
A known diesel engine that powers a motor vehicle has an oil pump that delivers oil under pressure to an oil rail serving electric-actuated fuel injection devices, or simply fuel injectors, that use oil from the oil rail to force injections of fuel. The pressure at the oil rail is sometimes referred to as injector control pressure, or ICP, and that pressure is under the control of an appropriate ICP control strategy that is an element of the overall engine control strategy implemented in the engine control system.
Certain known fuel injection devices contain electric-actuated valves that control the delivery of oil that has been pumped to an oil rail at ICP to pistons that force fuel into the engine combustion chambers via plungers. Examples are found in U.S. Pat. Nos. 5,460,329; 5,597,118; and 5,722,373.
Another example of such a device is disclosed in commonly owned U.S. Pat. No. 6,029,628. The device has a plunger that is displaced within a pumping chamber by oil from the oil rail to force fuel from the pumping chamber. The oil pressure elevates the fuel pressure within the device to a magnitude large enough for forcing a normally closed control valve at an outlet of the device to open. When that outlet control valve opens, the fuel pressure forces fuel through the outlet and into the corresponding combustion chamber.